This is old, but what the hell. There is a company I've seen several productions by that does all their shows in an outdoor amphitheatre, so they definitely use mics. When they did "South Pacific," Nellie just had her hair pinned up for the scene, and when she got in the shower she acted like she had put soap in her hair and went through the motions of washing it, then when she pulled the shower cord to rinse it, she really stepped behind the flow so that it splashed on the floor in front of her but she stayed dry. Afterwards, she "dried off" with a towel and wrapped her hair in it. It really looked just fine, especially from a little bit of a distance. She kind of got screwed out of one of the fun parts of doing the role (I feel the same way when Freds in OUAM don't actually get to go onstage wet), but it was necessary under the circumstances. From what someone in the running crew told me, the issue was partially the mic of course, but also that there was nowhere for her to go use a hair dryer after the scene.

I ran into this problem as well...and it was particularly hard for me because 1) they cut the dance break where I wash my hair in half and 2) my hair was down to the middle of my back and is very thick. So I had very little time to get it wet (forget even getting suds in it!). My goal was just that I wanted it to look wet because our theater is pretty small and people would be able to tell if I just pretended to get it wet. Plus like the last poster said, that's part of the fun of being Nellie! This was our shower:

So what I did was, I ran in as quickly as I could, took the ear part of my mic off (we have the skinny nude colored ones that wrap around your ear,) and hung it over the back of the shower. I did this facing away from the audience in a way that they could see, it just looked like I was preparing my hair for a shower. So the microphone pack was still on my waste, but the only part of the mic that was getting wet was the chord. Then I pulled the shower chord, quickly getting my hair as wet as I could in 10 seconds, and then quickly put the mic back on, grabbed my towel, and strutted back out. It was SO scary every night though because I wasn't always sure that I'd be able to do it in enough time!

_________________"I don't know about you, but I'd like to make today worth remembering."

I'm having my hair cut for Nellie as I think the intention is for me to full-on wash it on stage... also going blonde on the directors request! BUT I don't mind so much because I like doing things properly. I do like the idea of having Kelli O'Hara esque hair

If she is supposed to wash her hair I am not missing out on that!

Bit worried about the mic thing though!

_________________“Sometimes I can hear my bones straining under the weight of all the lives I’m not living”Extremely Loud and Incredibly Close - Jonathan Safran Foer